Soldato
I suspect they wouldn't come down in price even if the cards in question sold poorly. They would then make sure the cheaper cards had a limited supply, railroading buyers into purchasing the more expensive product, or having to go without. Most will hand over their money in that situation, and they know it.
If they weren't selling they would be forced into some kind of action. There's no way they would just stagnate and live on little to no income. You are right though, most people complain but buy anyway.